Nelson told colleagues Obama’s unpopularity has become a serious liability for Democrats in his state and blamed the president for creating a toxic political environment for Democrats nationwide, according to two Democrats familiar with his remarks.

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“It was a raucous caucus,” said one Democratic senator, who spoke on condition of anonymity because closed-door sessions are not supposed to be discussed with outsiders.

Nelson declined to respond when asked about the incident Thursday night, saying he was in a hurry to leave the Capitol to catch a flight. His spokesman didn’t return a request for comment.

In interviews after the marathon three-hour meeting, several senators and senior aides told POLITICO that Nelson was just one of several senators to express anger at White House missteps — and air deep concerns about their own political fates if Obama and the Democratic Party leadership can’t turn things around by 2012.

Added one veteran senator: “It was the most frank exchange of views I’ve ever seen.”

Several senators expressed the opinion that Obama needed to show more passion, while party liberals renewed their complaint that Obama should abandon the pretense of bipartisanship in the face of Minority Leader Mitch McConnell’s intransigence and what they consider the Kentucky Republican’s blatantly political tactics aimed at making Obama a one-term president.

Others said Democratic leaders need to clearly spell out what they believe are the motivations behind the Republicans' positions: that they are beholden to special interests, who bankroll their campaigns.

If Democrats keep losing the message war, they worry, they will be wiped out in 2012.

“There was a lot of passion in that room,” one senator said. “The reason is because the public is with us on our policies, but they’re not getting the message.”

Senate Majority Leader Harry Reid (D-Nev.), who along with House Speaker Nancy Pelosi and other Democratic leaders had met with Obama at the White House earlier in the day, calmly presided over the gripe session, sources say, allowing members to have their say.

Reid, who barely survived a challenge from tea party favorite Sharron Angle, has already taken steps to improve his own messaging operation, tapping New York Sen. Chuck Schumer to run the communications and policy operations of the Democratic Caucus in the next Congress.

With 21 Democrats and two independents facing reelection in 2012, Reid and the White House will be forced to deal with skittish Democrats eager to see a sharpened political operation.

But the complaints are not new. Over the past year, Senate Democrats have expressed dissatisfaction with Obama’s policy priorities, especially his determination to ram through a health care bill against the objections of party conservatives like Sen. Ben Nelson (D-Neb.). The caucus’s left wing, including Vermont independent Bernie Sanders, have argued the opposite point: that Obama’s timidity has led to the defection of liberals and young people turned off by Obama compromises on the public option and economic stimulus.

Thursday’s confrontation reminded some of a February 2010 showdown between Sen. Al Franken (D-Minn.) and Obama’s senior adviser David Axelrod after the president’s question-and-answer session with senators. An irate Franken, witnesses told POLITICO at the time, dressed down Axelrod and the White House for failing to provide a clearer sense of direction on health reform and other large legislative initiatives.